'''
Given a string, determine if it is a palindrome, considering only alphanumeric characters and ignoring cases.

For example,
"A man, a plan, a canal: Panama" is a palindrome.
"race a car" is not a palindrome.

Note:
Have you consider that the string might be empty? This is a good question to ask during an interview.

For the purpose of this problem, we define empty string as valid palindrome.
'''

class Solution(object):
    def isPalindrome(self, s):
        """
        :type s: str
        :rtype: bool
        """
        alphanumericS = [c for c in s.lower() if c.isalnum()]
        return alphanumericS == alphanumericS[::-1]


if __name__ == "__main__":
    assert Solution().isPalindrome("A man, a plan, a canal: Panama") == True
    assert Solution().isPalindrome("race a car") == False